Seventy Deadly Pills (1963)

A small boy, Dickie Goodwin, finds some strychnine pills mixed with sweets in a stolen car left in a deserted garage. With them he buys his way into the Rocket Gang. Brian, the leader, shares out the pills for swaps next day. One of the gang eats hers and collapses. The police frantically search for the pills and a broadcast appeal is made. Brian hears this and reaches the gang at Battersea funfair just in time to save them.